In what must be one of the most unlikely announcements ever made at a motor show, a sleek extended range EV coupé concept has been unveiled by... Cadillac.
Called the Converj and designed by British designer Simon Cox, the frankly rather impressive Cadi concept uses the same running gear as the Chevrolet Volt – now being called …

16kWh

Surely

Solar power for range extension

Even if those panels were 100% efficient they'd still be useless for propelling that car. They're useful for keeping some charge flowing into the battery and may give you the ability to drive onto a towtruck a week after you stopped. But that's about it. They also kick up the cost, the environmental impact and the weight of the car.

And yet the dumbass environmentalists will eat it up, insisting that it'll make a useful contribution to the car's range...

Still, good to see Cadillac making an effort (or helping show off the efforts of the rest of GM, anyway). You never know, they may even be able to handle corners in a few years! :P

"hundred od anxiety free miles"...

What this article doesn't mention is that this is a plug-in hybrid. It certainly isn't going to take you "hundreds of anxiety free miles" on one charge. A 16kWh battery is pretty puny - let's optimistically assume this hefty vehicle requires just 12Kw (10% of it's rates power) to push it down the road at a vaguely reasonable speed. It's going to run out of juice after about 80 minutes - not something that's going to take you hundreds of miles. In reality I suspect that you'd be lucky to get 50 or 60 miles on electricity alone.

Not to say it isn't a good idea, but please call it what it is - a plug-in hybrid. I suspect the roof-top solar array is an expensive gimmick unless you have some very strong sunshine where you live and don't travel very far.

Numbers

A 120kW motor and a 16kWh battery pack means it will only run at full power for 8 minutes. If it does 100mph at full chat, let's assume it can manage 50mph on a quarter of maximum power, ie 30kW. The 16kWh pack could provide 30kW for 32 minutes which would take you a little over 25 miles.

16kWh? Is that all?

So at full power the motor produces 120kW, so under full load the battery will last 8 minutes at best (though the motor won't be 100% efficient so it will be less). Doesn't sound like the endurance is going to be terribly good. Then when you knock off a kW or so for the air con it's not going terribly far at all.

A 50litre tank of diesel in my car is equivalent to about 488kWh, and I can go about 500 miles. So does that mean this caddy, all other things being equal, will go only 30 miles?

Vampires

Solar panel sunroofs and other GM spin

Ah, GM. How you spin. You spun your financials for a decade, even though anyone with a clue could see you were burning. You insisted that "bankruptcy is not an option" even unto the point where you took your begging bowls to Congress. You spun your so-called electric car, you spun your so-called hybrid technology (that you mostly licenced), you spun you spun.

And now you have a hybrid with solar panels that will give you extra range. Really? No, not really. Toyota is putting some on the new Prius, and they are honest enough to admit that it's just enough power to keep the AC running when sitting in traffic, that it has no bearing on the vehicle's propulsion.

But GM, you've been lying for so long, you don't even know how to stop.

This concept is a series plugin HYBRID

"impressive Cadi concept uses the same running gear as the Chevrolet Volt"

Please first read something about the Volt - here for example:

http://en.wikipedia.org/wiki/Chevrolet_Volt

This car is a series (plug-in) hybrid; it is propelled by an electric motor (120kW) which gets energy from the said 16kWh battery. When the battery runs down to a certain level (40% or so), the ICE engine starts and powers the generator, which provides electrical power to run the motor & recharge the battery. 120kW is the maximum power the motor delivers, the average power is in the 10-20kW range for normal city & highway driving. Even at 100mph, the needed power for such a car (dependent mostly on aerodynamic drag at high speeds) should be ~50kW. 120kWh is rigged for acceleration, not top speed in this case (see Tesla, which IS a pure EV, without ICE).

As for diesel fuel: the best &most efficient (automotive) diesel engines reach up to 40% efficiency in optimal conditions, but in real driving it is more like 20%, so from 50l of diesel, you only get ~100kWh of mechanical energy. This then translates to about 20kWh per 100 miles.

With those figures applied to the Cadi: 60% of 16kWh is 9.6kWh; at 20kWh per 100 miles, the Cadi can have a range of 48 miles on electrical power alone (and then the ICE engine kicks in to "extend the range"). 48 miles (or ~80km here on the continent) covers more than 95% of all daily driving (you can recharge the battery from the socket at night).

Solar power: a typical car occupies an area of about 8m2. If 5m2 (minivan with optimized roof area) can be covered with 20% efficient photo voltaic cells (current top Si cells), this is 1kWp of nominal solar cell power. Europe has equivalent solar irradiation of about 1000-1200h/year, so a 5m2 solar panel can produce up to 1200kWh of energy per year, which translates to 6000 miles on solar power alone per year. OK, this is theoretical figure, car has to be parked in direct sun every day, etc. (half of this is more realistic), but shows the right direction. As for cost: yes, the solar cells are expensive, but have a life time of 30+ years. And the (extremely expensive for now) Ge based cells reach 30+% (40.7 current lab record using concentrated sun light) efficiency. Think about solar cell covered park lots - provide power & shade to cars at the same time.

As far as the ICE engine goes: GM plans to use the familiar 1.4l Ecotec engine, currently spinning in a lot of Astras, Corsas, Merivas, etc. (they first vanted to use the 3 cylinder 1.0 12V engine).